1. Field of the Invention
The present invention relates to a shaft for mounting an article having a center hole. An article mounted on a mounting shaft through a hole formed in the center thereof is likely to move or rock in some direction under the influence of various external forces acting on the article. Such a rocking motion prevents smooth operation.
One example of such a problem will be described with respect to a roll paper mounting shaft for a printer unit of a continuous photo-processing machine. A cylindrical core for roll paper or a cylindrical core of a magazine, which is adapted to contain roll paper and is widely used nowadays in order to obviate an accidental exposure of the paper to light, is mounted on a cantilever mounting shaft fixed to a printer frame. The roll paper mounted on the mounting shaft is pulled out in a long strip during the process of print treatment. Any large deflection, particularly rocking motion, in the axial direction of the mounting shaft is likely to cause a strain to be imparted on or snaking of the roll paper which has a detrimental effect on the printing operation in which high accuracy is required.
2. Description of the Related Art
Various types of mounting shafts have been proposed which are adapted to minimize unexpected rocking of the article mounted on the mounting shaft. A conventional mounting shaft is provided with one or more panel springs extending axially on the surface so that when an article is mounted thereon, the top of the spring will be pressed against the inner wall of the cylindrical core of the article, while the height of the spring above the surface of the shaft is reduced. Another conventional mounting shaft is provided with one or more elastic annular bodies mounted on the periphery of the shaft and a tapered member adapted to be forced in between the elastic annular bodies and the mounting shaft so that the former will be radially expanded and pressed against the inner wall of the cylindrical core of the article to support it.
The former prior art mounting shaft has an advantage that its mechanism is simple. But, because of a high elastic force exerted by the arcuate springs, considerable power is needed when mounting the article on and dismounting the article from the mounting shaft, thus imposing a great deal of load on the article locally. If, for example, the roll paper to be printed is mounted on the former prior art mounting shaft, the roll paper wound around a core in a cylindrical shaft is liable to be telescoped since the roll paper is pressed against the mounting shaft locally, thus causing a slight change of position of the roll paper with time. On the other hand, with the latter prior art mounting shaft provided with the expandable elastic annular bodies around its periphery, a fine adjustment is required according to any error in the inner diameter of the cylindrical core of article. Consequently, it is difficult to expect versatility from this type of mounting shaft. Furthermore, on account of a great number of components being required and its complicated mechanism, the mounting shaft could easily malfunction and could be costly. Still further, since the area of contact between the elastic bodies and the core of the article is relatively small, it is difficult to reliably eliminate the axial deflection of the article.